Joint Operation of Surface and Groundwater to Improve Sustainability Index as Irrigation System Performance: Cyclic Storage and Standard Conjunctive Use Strategies

Abstract

A cyclic storage (CS) system is an extension to standard conjunctive use (SCU) of surface water (SW) and groundwater (GW) in which the SW bodies and GW aquifer(s) are treated as physically interconnected and operationally joint parallel storage facilities. Rule-based exchange of regulated water between surface reservoir(s) and GW aquifer(s) is the key element of a CS system that differentiates it from the SCU of SW and GW as usually practiced. This paper presents a novel multiobjective optimization model to develop a tradeoff between the sustainability index of water allocation to irrigated agriculture and energy required for GW pumping. The sustainability index, as defined in this paper, addresses reliability, vulnerability, and resilience. A solution to the large-scale multiperiod, multiobjective, mixed-integer nonlinear model was obtained using the ε-constraint method. The model maximizes the sustainability index while keeping the pumping energy at its minimum. Results show that CS operation strategy considerably improves the sustainability index compared to the SCU strategy. It is also shown how, for a given sustainability index, the required energy for pumping GW would decrease. Results may help decision-makers identify optimal policies and assess different policies under CS and SCU strategies. Agricultural-sector and system operators must become familiar with the predominance of CS over SCU for its real-world application.